38 J. J. STEVENSON — CARBONIFEROUS OP APPALACHIAN BASIN 



Introduction 



Id a former memoir* the writer described the Lower Carboniferous 

 or MississippiaD of the AppalachiaD basin. Id this the effort will be to 

 describe the lowest formation of the Coal Measures or PennsylvaDian of 

 the same basin. 



The Coal Measures were studied in detail first in the Virginias and 

 Pennsylvania by Professors William B. and Henry D. Rogers, who 

 divided them into five groups, uumbered XII, XIII, XIV, XV, and 

 XVI, and afterwards named 



XVI. Upper barren group. 



XV. Upper coal group. 

 XIV. Lower barren group. 

 XIII. Lower coal group. 



XII. Serai conglomerate. 



This grouping, based origiually od somewhat arbitrary grounds, proved 

 so conveDient that it was accepted by most of those who have written 

 on the northern portion of the Appalachian basin. In accordance with 

 later usages, geographical terms were introduced by the Pennsylvania 

 geologists. Those which have the priority are 



Dunkard of I. C. White, 

 Monongahela of H. D. Rogers, 

 Conemangh of Franklin Piatt, 

 Allegheny of J. P. Lesley, 

 Pottsville of J. P. Lesley, 



these being equivalent to the divisions as made by the brothers Rogers. 

 The literature is extensive, as the Coal Measures of the Appalachian 

 basin early attracted investigation ; but the limits of this study make 

 necessary the use of only the later studies, which superseded those 

 made by the older geologists under less favorable conditions. 



Pottsville of Lesley: Seral Conglomerate of Rogers 



nomencla tube 



The Seral conglomerate of Rogers is between the Mauch Chunk red 

 shales below and the lowest bed of the Allegheny above. The forma- 



* Part I, " Lower Carboniferous of the Appalachian Basin," was published in this Bulletin, volume 

 14, pp. 15-96. The writer desires to acknowledge his great indebtedness to Dr I. C. White and 

 Mr David White, who have granted without reserve all his requests for information. It must be 

 understood that this statement does not commit either of those observers in favor of the writer's 

 conclusions. 



